Charged particle beam systems employed for inspection and/or imaging purposes typically generate a primary beam, of electrons or ions, which is focused onto the surface of a specimen by a charged particle beam column. The detection process generally involves the collection of secondary electrons, secondary ions, backscattered electrons and/or backscattered ions, which are emitted from the specimen surface as a result of the interaction of the primary charged particle beam with the specimen Additional detection configurations (as described in U.S. Pat. No. 7,417,235) disclose the detection of tertiary electrons and/or tertiary ions emitted from any surface within the detection system (other than the surface of the specimen) due to impingement of backscattered electrons and/or backscattered ions, neutral atoms or other particles thereon.
In order to inspect or form an image of the specimen, it is advantages to selectively detect charged particles produced due to operation of a charged particle beam column irradiating a specimen.
For example, a dual detector optics system for simultaneous collection of secondary and backscattered electrons is disclosed in U.S. Pat. No. 7,227,142. This detector optics system is a part of an electron probe system used for the testing of large substrates during manufacture. The design of the detector optics utilizes a field-free tunnel and substrate electric-field control electrodes to enable separation of the SEs and backscattered electrons into two detectors, allowing simultaneous acquisition of topographic and elemental composition data, with minimal impact on the electron probe.
It is generally desirable to reduce the number of detectors in any electron or ion beam system. Multiple detectors increase system cost and occupy space in the vacuum system, which may be needed for specimen manipulations. A detector capable of detecting secondary electrons, backscattered electrons, secondary ions and backscattered ions would therefore free space and significantly reduce manufacturing cost, provided the detector can distinguish between those particles by means of preferably automatic manipulation of voltages only, rather than mechanical adjustments or other direct operator intervention.
U.S. Pat. No. 7,417,235 describes a multi-purpose efficient charged particle detector that by switching bias voltages can detect either secondary ions, or secondary electrons from a specimen, or tertiary electrons that originate from backscattered electrons. The particle detector comprises a sparse collecting electrode; Venetian Blind strips for converting secondary ions to electrons disposed behind the sparse collecting electrode. The particle detector further comprises at least one further electrode adjacent the Venetian Blind strips and a scintillating disc for producing scintillation photons upon impingement of energetic electrons.